Telephone system



Jun. 9, 1931.l R KRUSE 1,809,046

TELEPHONE SYSTEM Filed April 30, 1930 3 Sheets- Sheet l RUEE Kruse' -June 9, 1931. R. KRUsE 1,809,046

TELEPHONE SYSTEM Filed Aprilso, 19:50 s sheets-sheet 2 Embf Krus E MM June 9, 1931. R. @USE 1,809,046

- TELEPHONE SYSTEM Filed April 30, 1930 3 Sheets-Sheet 3 Patented June 9, 1931 inane Parser ortie noBERr KRIS, or inLriv, GERMANY, Assis-Non rro siemens a transita narran- GESELLSCHAFT, or wneivnnwnnx, sinnnivss'ranr, Naan Bastin, GERMANY TELEPHONE SYSTEM p'pliction l'd April 30, 19,30, Serial No. 448,486, and in Germany June 12, l929.

The invention relates to a. circuit arrangement for party lines inv communication system-s, especially telephone systems.

One object is .to effect without any special switching operation for that purpose, the marking engaged of the junction line immediately the latter is seized, this marking engaged being requiredA to keep the conversation secret, and is etfectedby causing switching devices to function when the connecting line is seized, whereupon by transmitting alternating current they automatically prevent branch-off stations being connected to this connecting line.

Another object is to setup in the simplest manner a connection with other' party lines over the calling party line. This is achieved in that a storer is associated with the p-arty line, and when the stations call one another the storer positions the switches at Vthese sta-tions, and when the' designating number of another party line is selected it directly brings about the connecting up of the other party tothe calling party line.

Another object is to effect uniformity in the construction of communication systems more especially telephone systems with storing devices by enablin'gthe storing devices to be easily adjnstedto the'difterent damping of the connecting lines' (lines of different lengths) and to the type-s of switches used. This is achieved by providing the storer with switching devices, which enable analteration to be eiected in the speed at which the current impulses are given on by the storer.

Another object is to associate the party lines with a large number of subscribers7 lines stations, without having to divide the latter into groups. This. enables simple switches and more especially small impulse senders (l0 point number dials) to be used, thereby in the latter case are avoided great difficulties in connecting a party line to an exchange tted with automatic connecting devices built up on the decimal system, because the subscribers stations can use their impulse senders inthe same manner for callsv a decimal grouping and are sent out `from a calling subscribers station for selecting a station belonging to the calling subscribers line, and the said translator then gives ott number impulses in uninterrupted succession for the purpose ot reaching the wanted subscribers station.

Another object is, when high value connections are to be set up and the party lines are engaged by low value connections, to com pulsorily release the low value connection by disconnecting all the stations of the party line, in order to render the conversation secret. This is achieved in that after the seizing of a party line, which is already engaged by a low value connection, for a high value connection to a station oiz that line, switching means come into action and canse switches, which are located at each ot thc stations to be positioned into a resting position (normal or blocking position).

@ther objects pertaining to the detailed circuit arrangement will be apparent from the following specification.

The invention is illustrated in the accompanying drawings, comprising Figs. l to 3, inclusive. The various sheets shonld be joined together, with Fig. l to the left oi Fig. 2 and Fig. 3 to the right of Fig. 2.

Figs. l and 2 togetner show by means oft the usual schematic diagram, the switching device in the exchange accessible to `the party line serves to receive the current impulses transmitted by the calling subscriber as well as to store them up and to transform them; it also effects the sending back of the impulses into the party line for the purpose of connect-ing up the wanted subscriber', this being effected by operating the stepping switches individual to the dirferent stations.

F or this storin0` and translating are nsed for example two stepping switches; of these the storer l, which is the first to be positioned, is constructed like a first preselector having 5 Contact segments and therefore also 5 wipers c, b, c, d, e, and the storer 2 like a side switch likewise consists ot' 5 contact segments, which are insulated from one another and are bridged over by the wipers in the corresponding positions of the storer when the latter is positioned. The wiring of the storers can easily be seen from the ei;- ample shown. The running-oliq of the storer is etlected by a relay chain, alternating current impulses being at the same time sent over the party line for connecting up the wanted subscriber.

The trunk exchange FA has access to the party lines and the relay C is energized in some manner to place the impulse receiving relay A under control oi the trunk exchange FA by closing contact 1470. The impulse transmission for connecting up the wanted subscriber is eilected in the saine manner, by the trunk exchange FA, as the regular calls.

The line H shown in the upper part ot Fig. 1 is another subscribers party line similar to line VT Fig. 3'shows the party line subscribers station equipment. ln the present example stepping switches are provided at every subscribers station. They can be controlled from the device iitted in an exchange accessible to the party line. The stepping switches at the different stations function in such a. manner that when tl ey leave their normal position they operate certain contacts and when they reach certain positions corresponding to the connected up stations they operate other contacts. At the subscribers station T these contacts function in the tollowing manner: The wiper 2O s touches the contact segment as soon as the first stepv is taken; the wiper 6 s leaves the contact segment for example at the last but one step, which in the present example is the 31st step; while the wiper 9 s opens its Contact as soon as it leaves the normal position; the the other wipers 10 s, 11 s, and 17 s only efiect a circuit closure at the position of the stepping switch corresponding to the respective station.

The relays R, R1, etc., are shunted across the conductors a-b of connecting line VL and receive the alternating current impulses sent out from the device in the exchange, for stepping the rotary switches at each subscribers station.

Subscribers stationv T1 and any other subscribers station on the line will have the` same equipment as station T, but wired to different contacts of rotary switches.

Relay D is thc rota-ry magnet for stepping the rotary wipers and Vf is the subscribers bell which is cut out of circuit when the subscriber answers.

A @all between two subscribers on the 8eme party Zine As an example ot the invention will be described a connection between the subscriber T of a party line and thesubscriber T1 of the saine party line.

ViThen the subscriber T takes down his receiver, the contacts of his switch-hook are operated, that is to say the contacts 13 7m and 15 7m are opened and the contacts 14E 7m and 16 im are closed. The elo-sing of contact 16 7m energizes the relay U 2 over: earth, contact 16 hu, relay U 2, wiper 9 3 of the stepping switch, contact 5 j,'wiper 6 s of the stepping switch, relay J, battery, earth. For want of sufficient current the relay J is not operated in this circuit.` On being energized the relay U 2 closes the contacts 1 a 2, 2 u 2, 8 u 2, and 12 a 2; thereby the leads a and b of the connecting line VL are bridged over at the subscribers station T and in addition the relay U 2 is placed in a locking circuit. Thereupon the relay A located in the eXchange accessible to the party line is energized over: earth, battery, winding T of relay A, contacts 141 c, 21 w 1, 135 lead a of the connecting line VL, contact 1 u 2, subscriber T, contact 2 u 2, lead Z) of the connecting line VL, contacts 133 23 w 1, winding II of relay A, earth. Relay A operates its contacts hence relay V is energized over: earth, contacts'29 w, 30 a, relay V, battery, earth. Thereupon the relay Z is energized over: earth, Contact 31 o, relay Z, battery, earth; and the relay U is energized over: earth, battery, rotary magnet D 1 of the storer 1,-wiper s 1 of the storer 1, relay U, contact 91 o, earth. In addition the relays S and R are energized over: earth, contact 30 o, wiper 132 a 2 of the storer 2, windings I o the relays R and S, battery, earth. By closing its contact l56 u, the relay U energizes the relay W 1 over: earth, battery, relay lV 1, contacts 56 u, 57 u 1, 58 p 1., 59 o, earth. The relay lV 1 opens its contacts 21 'w 1 and 23 lw 1 and closes its contacts 22 fw 1 and 2A w l. The opening of the said contacts disconnects the relay A from the loop extending over the subscribers station, and it therefore falls back. Thereupon the relay l-l is energized over: earth, battery, relaf; lll, contacts g, 79 fv, 78 a, 76 w, earth. "Upon being energized, the relay H closes a (im. uit forr energizing l the relay M over: earth, battery, winding Il of relay M, contacts 62 g, 63 7L, 65 o, earth. By closing its contacts 26 m and 26 m, the relay M applies alternating current to the leads a and o of the connecting line VL, which operates the alternating current relays (R, R1,) located at the different telephone stations. The energizing or'I relay R causes the relay J to'be operated in the station T and in corresponding manner in the other stations, the devices for the latter are not shown here, as they correspond to those of the station T. The energizing circuit for the relay J extends in the station T over: earth, contacts 7 r, 5 j, wiper 6 s of the stepping switch, relay J, battery, earth. Relay J now independently of the relay contact 7 r holds itself over: earth, contact 4 Z of the rotary magnet D of the' steppin@ switch, 3 j, relay J, battery, earth. On being energized, the relay J at its contact 19 operates the rotary magnet D of the step.- ping switch, which is moved on one step and therefore opens the contact at its wiper 9 s. Nevertheless the relay U 2 remains energized because the contact opened at wiper 9 s is bridged over at Contact 8 u, 2 when relay U 2 is operated. As, however, at all the other. stations except the calling station the relays corresponding to relay U 2 havenot been energized, it is impossible for the other subscribers of the party line to operate their relays U 2 with their switchhook by taking down the receiver, and thus it is impossible for them to connect themselves to the common line. Hence the taking down of the receiver at the calling subscribers station causes the automatic blocking of all other subscribers stations belonging to the party line.

If we now consider the further circuit changes in the exchange, will see that after the relay M has been operated and has caused the alternating current impulse to be sent out, the relay Q is energized over earth, battery, relay Q, contacts 68 m., 65 e, earth. Relay Q places itself in a locking circuit over: earth, battery, relay Q, contact 69 g, 79 o, 78 a, 76 w. The opening of contact 7 O g deenergizes the relay H, and the opening of contact 62 g deenergizes the relay M. Here it should also be mentioned that upon the operation of relay M, the relay U 1 is also energized over: earth, battery, winding H of relay U 1, wiper 51 s 2 of the storer 2, contacts 54 m, 53 o, earth. Relay U 1 places its winding H in a locking circuit, which extends over contact 52 u 1 after relay M has been released and has opened the contact 541 m.. On being energized, the relay U 1 at Contact 57 u 1 opens the circuit for energizing the relay W 1, hence the subscribers loop is again switched through to the relay A in the exchange. The relay is again operated and at contact 78 e deenergizes also the relay Q.

As we have seen at the transmission of the alternating current impulse the relays H, M and Q operate in an energizing chain. These relays serve for impulse correction, because, owing to the long connecting lines, the relay A does not work with the required uniformity of impulse succeeded by pause. This irregular working isV corrected by the relays M, Q and H, and a uniform impulse relationship is created.

After the relay U 1 has been energized, the relay D is operated over: earth, battery, differentially connected and parallelly located windings I and H of relay D, contacts 129 u, 130 u 1, 131 v, earth. Owing toits differential action, the relay D is operated slowly, the delay being so adjusted that it is not operated until the correcting chain of relays M, Q and has functioned once, the object being to prevent a premature actuation of the storers, the connecting up of the latter being dependent on contact 86 Z of relay D.

After the stepping switcheslat the different telephone stations have been moved on, the relays A, V, Z, R, S, U, U 1 and D are therefore energized in the exchange. Vhen the calling subscriber now transmits number impulses for the purpose of connecting up the wanted subscriber, he interrupts at each im pulse the loop over the a and b leads of the connecting line, and thereby the relay A in theexchange is released and pulled up again in accordance with the interruptions of the loop. The impulse correcting relays H, Q and M now work in accordance with the numerical selection sent out by the subscriber, and do so under the control of the impulse receiving` relay A. The correcting chain of relays M, Q vand H is controlled over the contact 78 a in the `manneralready described in the description of the first alternating current impulse for moving on the stepping switches from their normal position. Thus by the contact 78 a is operated the relay H, by the relay H (Contact 63 7L.) the relay M and by the relay M (contact -68 m) Athe relay Q;the latter then causes the entire correcting chain to fall back by opening the contacts 62 g, 70 g, so that the relays'can be again operated by the impulse contact 78 a. We see therefore that every relay of the correcting chain is operated in accordance with the impulses of the impulse receiving relay A; hence also the storer 1, the rotary magnet D 1 of which is controlled by contact 87 g, is operated in accordance with the impulse train transmitted from the subscriber. Theref fore if the transmitted impulses consist of 4 impulses, they operate therotary magnet-D 1 of the storer 1 four times over: earth, bat-V tery, rotary magnet D 1 of storer 1, contacts 98 u, 85 u 1, 86 d, 87 g, 88 e', earth. Therefore the storer 1 is positioned onto the fourth step as is shown in the drawing; it has already been said that this storer corresponds to a known preselector. 1

The relay U falls back at the end of the first train of impulses; during these impulses it was maintained energized over; earth, battery, resistance 72' 1, contacts 89 g, 90 u, re-A lay U, contact 91 c, earth. YOn falling bacl;

the relay at its contact 92 u effects a switching over from the rotary magnet D 1 to the rotary magnet D 2 of the storer 2; therefore the second impulse train, which Vis assumed to comprise 2 impulses, now acts on the rotary magnet D 2 of the storer 2 and twice operates it over: earth, battery, rotary magnet D 2 of the storer 2, contacts 92 u, 85 u 1, 86 d, 87 g, 88o, earth. Accordingly the rotarymagnet D 2 advances the storer 2 two steps, so that its wipers bridge-over the vstep 2 in each segment, this being shown by dotted vlines in the figure. Y

At the end of the second impulse train the relay U 1 falls back; during the second impulse train it wasmaintained Venergized over: earth, battery, winding I of relay U 1, contacts u 1, 54 m, 58 '0, earth. Thereupon the relay IV is energized and owing to its two windings being i dilerentially connected, like the relay D it is slowly operated over: earth, battery, parallelly located windings I and II of relay TVV, contacts 127 u, 57 u Y 1, 58 p 1, 59 c, earth. Furthermore the relay D is released by the opening of contact 130 a 1, and after the relay `W has been operated, the relay XV 1 is energized over: earth, battery, relay `W 1, contacts 128 w, 58 p 1, 59 fv, earth. The energizing of relay W causes the relay chain consisting oit' the relays H 1, H 2, H 8, H 4, H 5, and P to be started up for running oil the positioned storer, and during this running off, alternating current is sent over the party line and the contacts of the relays WV 1 and M for connecting up the Wanted subscriber.

During the reception of current impulses transmitted by the subscriber, the relay A functioned as an impulse receiving relay, and during the running off of the storer it functions as a beating relay in the relayY chain for sending impulses over the party line. In addition to the impulse correcting relays M, Q and H, there also functions now the relay O, which together work as impulse beating` relay; and they do so in such a manner that the relays M, O, Q, and H by their interaction uninterruptedly Adetermine the length ofthe opening and closing of the impulse circuit.

The speed of the impulses must be adjusted to the length of the lines and to the type of stepping switches used, so in order to obtain the simplest possible arrangement for adjusting the speed of the impulses, during the running-off of the storer, the relay O is provided with a. second winding, which is short circuited at each impulse over a contact of this relay during the sending back of the impulses. The duration of the contact make can be increased or decreased in simplest manner for example by means of an adjusting screw on the contact 66 0, hence the duration of the short circuiting of winding II otrelay O can be varied. rlhis renders it easily possible to alter the giving of the impulses in accordance with the given conditions, so that for example in the present example this spe-ed of impulse transmission can lie between 4 the limits of 9 and 18 interruptions per with the aid ot a contact of relay M (26 m and 28 m) it sends current impulses over the party line.

The relays R and S, which, as already said, were energized as soon as the exchange was taken into use, place themselves in a locking circuit, thus the relay S is locked over its contact 84 s and winding I, while relay R is oclred over its winding II by the contact The storer is run-off by the chain of relays H 1, H 2, etc. in the following manner: After the relay WV has been operated, the relay H 1 is energized over: earth, battery, relay H 1, contacts 98 7L 2, 96 e, 95 L, 94 fw, earth. The relay H 1 places itself in a locking circuit over: earth, battery, relay H 1,

contacts 100 h 1, 109 p, 110 o, earth. The operating of relay H 1- causes the relay H to be energized over: earth, contacts 77 w, 75 h 1, 74 p 1, 73 p, 72 0,70 g, relay H, battery, earth. The closing of contact 114 It energizes the relay A over: earth, battery, winding III of relay A, contacts 112 fw, 125 5, 114 7L, 117 p 1, 118 j), 119 c, earth. The energizing of relay H causes the relays M, Q, and O to be energized in succession as has already been described for the relays M and Q, when the number impulses were received. After they have mutually controlled each other, they again release relay H,`so that the opening of contact 114 h causes the relay B to be energized over: earth, battery, winding III of relay A, contacts 112 w, 125 b, winding II of relay B, contacts 115 a, 117 p 1, 118 p, 119 a, earth. Relay A remains energized in this circuit, while at the same time the closing of Contact 126 Z) establishes a locking circuit for relay B over winding I. Y

An alternating current impulse is sent over the party line the irst time the relay H is operated, because the contacts 28 m and 26 m are closed by relay M when the latter is energized over contact 68 7L by relay H. At the sam-e time the test relay P l over contact 34 z, is applied to the odd steps of the contact segment 1 of the storer 2, the circuit extending over: contacts 89 r, 86 Z), 35 u 1, 84 7L, relay 1, battery, earth.

The second alternating current impulse is sent out the second time the relay H is operated, While at the same time the test relay P 1 is applied to the even steps of the contact segment 1 of the storer 2, because now the relay B, which was energized the first time the relay H fell back, has now closed its contact 37 b, namely over: segment 1 (even steps), contacts 40 r, 37 35 u 1, 34 7L, relay P 1, battery, earth.- As no potential has been applied to the contact segment 1 of the even and odd steps, the relay P 1 is not energized. The second time the relay H pulls up, the relay A is released owing to the opening of contact 118 7L.

The relays D and E work under the control of relay A in the same manneras relays A and B work under the control of relay H because the first time the relay A pulls up and therefore also the first time relay H pulls up, the relay D is energized over: earth, contacts 119 o, 118 p, 117 p 1, 121 a, 122 e, 124 fw, windinglH of relay D, battery, earth. The iirst time relay A falls bach (that is second time relay H pulls up) the rela;Y is energized over: earth, contacts 119 o, 118 p, 117 p1, 116 d, winding I of relay E, contacts 122 e, 124 w, winding H1 of relay D, battery, earth. Relay E places its winding H in a locking circuit over Contact 123 e.

Then relay H falls back for the seconr time, relay H 2 is energized over: earth, battery, relay H 2, contacts 102 /L 3, 97 95 7L, 94 fw, earth. The locking circuit of relay H 2 extends over: earth, battery, relay H 2, contacts 101 7L 2, 109 p, 110 fz), earth. 1n addition, the relay B is deenergized by the opening of contact 114 7L.

Then the relay H is energized for the third time, as at the rst energizing the test relay is applied to the odd steps in the segment 1 and in similar manner the relay A is energized, which by` opening its Contact 120 cz now deenergizes the relay D.

Then the relay H falls baclr for the third time, the relay B is operated like at the first deenergization and it closes its contact- 37 b, hence the fourth time the relay H pulls up the test relay P 1 tests the even steps of segment 1.

Then the relay H is energized for the fourth time, the relay A falls back like it did at the second energizing of relay H, therefore also the relay E is deenergized by the opening of the contact 121 a..

The fourth time relay H falls back, the opening of the contact 114 7L deenergizes the relay B and also energizes the relay H 3 over: earth, battery, relay H 3, contacts 104 7L 4, 99 L 2, 96 e, 95 7L, 94 w, earth. The relay H 3 locks itself over its contact 105 It 3.

Then the Vrelay H is energized for the iifth time, the just-described operations for the relays A, B, D, and E are repeated, so that at the sixth release of relay H the relay H 4 is energized and at the eight release the relay H 5 is energizechthese relays placing themselves in corresponding locking circuits.

At the ninth energizing of relay H, the relay A is again energized and thus also the relay D. Y y

At the ninth release, the relay B is energized in the manner already described; hence at the tenth energizing of relay H the test relay P 1 is connected for the tenth time to the segment 1. At the same time the relay A is deenergized and then again causes the relay E to be energized. The tenth time relay H falls back, it causes therelay P to be energized over: earth, battery, relay P, contacts 108 h 5', 103 h 3, 97 e, 95 k, 94 fw, earth. The relay P @pentes its contante and this brings about the following circuit changes: The opening of contact 7 3 p brings the relay chain H, M, el, O into the initial condition, in the same manner as the relays H 1, H 2, H 3, H 4, H 5 by the opening of contact 109 p. The opening of contact 118 p also brings the chain of relays A, B, D, E into the normal position. 1n addition the locking circuitl of relay R is opened by the contact 82 p. During the momentary opening, the relay holds up owing to its winding 11 being short circuited. The closing of the contacts 38 fr and 41 7" prepares the test circuit for the relay P 1 for the segment 2. y

After the relay P has also fallen back when relay E has been deenergized, the operations are repeated in the same manner at the segment 2. 10 impulses are transmitted again by live times testing the even and odd steps of segment 2. After they have run off, the Venergizing of relay P again causes the relays H l-H 5 of the relay chain to be deenergized. The relay S is now also deenergized, because it does not act slowly when contact 82 p is opened, as the short circuit has been removed by the Contact 81 1". Therefore the closing of contacts 42 s and 44 s places the relay P 1 at the disposition of segment 3 of the storer 2. Also at the running over ofthe odd steps in segment 3 for the first time, the relay P 1 is not yet operated,because,although the relay H1 has already closed its Contact 46 h 1, the first step has not been bridged over. This only occurs when` the relay H has been operated for the second time, that is to say at the second impulse after the segment 3 has been reached when the even steps are being tested and then an energizing circuit is closed over the bridged step 2. This circuit extends over: earth, contact 46 7L 1, storer 1, step 2 (storer 2), contacts 44. s, 41 37 b, 34 it, relay P 1, battery, earth. By closing its contact 32 p 1, relay P 1 places itself in a locking circuit and'so by opening contact 74 p 1 prevents the relay H being again energized and thus also prevents the common relay chain being energized again; hence no more alternating current impulses are sent over the party line. Furthermore the relays A, B, D, E are deenergized' by the opening of contact 117 p 1. 'A T e can see from the description that there are transmitted ten impulses when segment 1 is run over, ten more impulses are Vtransmitted for segment 2 and two impulses for segment 3, thus a totalof 22 impulses in place of the subscribers numerical selectionV 4, 2 are transmitted. r1`he 22 impulsesmo've von all the stepping switches 22 steps, but in the position 22 only at the wanted station are closed the corresponding contacts, so that the contact corresponding to the wiper 17 s closes a circuit for the bell T to call the subscriber. On taking down the receiver, the closing of the Contact at the wipers corresponding to -I the wipers 10 s and 11 s causes the energizing of the relay corresponding to the-relay U 2, thus bringing about the connecting up of the wanted subscriber.

The already-described energizing of relay P 1 causes the relays W and W 1 to tall back when the contact 58 p 1 is opened, hence the closing of the contacts 21 w 1 and 23 fw 1 causes the speaking connection to be fed over the impulse receiving relay A.

TVhen the subscribers loop is opened at the end of the conversation, relay A falls back and after a little while eiiects the release of the slow-acting relay fv, which after a while causes the very slow-acting relay Z to fall back. During the interval between the falling back of relay V and the release of relay Z a circuit is established for the relays M and 71 over: earth, contacts 60 e, 61 o, windings operated), battery, earth.

I of the relays M and W 1, battery, earth. The closing oi the contacts 22 w 1 and 24 w 1 as well as contacts 26 m and 28 m causes alternating current to be applied to the party line, thereby bringing about the return of the step-by-step switches. The storers 1 and 2 are also returned to their normal position in some manner of no interest here.

A @all from a subscriber on one party Zz'ne to a subscriber on mot/lier party Zine impulse receiving relay of the other traffic direction (linel), Relay A is maintained energized over the contact 149 :a Relay P 1 is maintained energized over the closed contact 148 and prevents the storer runningof. The energizing ofthe impulse receiving relay in line II, which correspondsto the relay A, brings about the same operations as took place when relay A was energized, namely one energization of the relay corresponding to the relay V, and thereby an energization of the relay corresponding to relay Z, hence the relay X is maintained energized 'over earth,

contacts 150 e II, 139 o H, 140 an, relay X etc. as already described Jfor the energization of the relay X. l

The impulse trains subsequently transmitted then influence switching devices on the other line.

The release takes place in such a manner that first of all upon the release of the impulse receiving relay in line H there takes place the same circuit changes as when relay A was deenergized; that is to say, the relay in line II corresponding to the relay V is first deenergized, and by opening the contact 139 o II it releases the relay X, which at contact 149 m opens the locking circuit of relay A, hence the already-described release is thereby brought about.

Toll oem'ng service If the party line seized as described for a low value connection is reached by the trunk exchange FA for setting upa high value connection, the trunk exchange on reaching the party line will over the leads a 1 and b 1 notiy the subscribers that there is a high value connection to be set up. By applying an earth to the lead c 1, the relay C is energized, which by closing its contact 147 c connects winding I of relay A to the lead a 1 and'by closing the contact 146 0 connects the relay T to that lead.

In some manner or'otherthe trunk exchange now gives over the lead a 1 an earth current impulse, whereby the relay T is energized and at contact 143 t it opens the locking circuit of the relay A. Thereby the relay V is deenergized (by the opening of contact 30 a), and as the very slow-acting relay Z is still energized, it brings about the release of all the stepping switches because a long alternating current impulse is Vsent into the party line owing to the relays M and W 1 being en-l ergized over: earth, battery, windings I of the relays M and WV 1, contacts 61 o, 60 a, earth. The alternating current impulse for some time operates the relays R, R 1, etc. therefore the J relays are energized over: earth, battery, relay J, wiper 6 s, contacts 5 y', 7 1^, earth. Relay J with its contact 19 7 operates the rotary magnet D, which at its contact 4 cl interrupts the locking circuit of relay J thus the relay J and rotary magnet D iiiteract. This continues until the wiper 6 A leaves the contact segment at the 31st step, so opening the circuit for energizing the relay J.

If the subscriber T has not yet hung up the receiver, the stepping switch of the subscriber T remains in the position 31, which is the blocking position. If the receiver has already been hung up, the relay J is maintained energized over: earth, contacts 7 r, 13 im, position 31 of the wiper 6 s, relay J, battery, earth, until the end of the alternating current impulse, and only then is relay J deenergized while at the same time the energizing circuit of the rotary magnet D is opened, whereupon this rot-ary magnet moves on the stepping switch into the initial position.

As soon as the compulsory release has been effected, that is'to say when relay T has fallen back, the relay A is energized over leads a 1 and b 1 looped in the vtrunk eX- change FA, whereupon an alternating current impulse is sent out for blocking the VllO party line for other calls in the same manner as when this is doneby the energizing of relay A when a` subscribers station of the party line originates a call.

lhat is claimed is:

l. In a telephone system, a party line having a plurality of subscribers stations, a switching device individual to said party line and capable of transmitting an impulse over said line, and means responsive to an impulse from said switching device for automatically preventing the said subscribers stations from seizing said party line.

2. In a telephone system, a party line having a plurality of subscribers stations, a switching device individual to said party line and capable of transmitting an impulse over said line, means responsive to one of said subscribers stations seizing said party line for said switching device to send an alternating` current impulse over said line, and means responsive to said impulse for preventing any other subscribers stat-ions on said line from connecting thereto.

8. In a telephone system, a party line having a plurality of subscribers stations, a switching devic-e individual to said party line and capable of transmitting alternating current impulses over said line, a relay mechanism and a stepping switch individual to each of said subscribers stations and all i sponding in synchronism to alternating cu rent impulses from said switching device tor selecting the wanted subscribers station.

4. In a telephone system, a party line having a plurality of subscribers stations, means responsive to one oi"- said subscribers stations seizing said party line for sending an alternating current impulse over said linD for preventing any other subscribers sta-tions from being connected thereto, and means responsive to said subscribers station dialling the numberk of another subscribers station on said line for sending out alternating current impulses for connecting said other subscribers station thereto.

5. In a telephone system, a party line, individual switches for the stations on said line, means at the exchange for registering a number dialled by one ot the stations, a sender controlled by the registering means :tor transmitting impulses back over the line to operate said switches, said-sender including interrupter relays for generating impulses, and means for regulating the restoring time of one of said rela-ys to adjust the rate at which impulses are transmitted.

6. In a telephone system, a party line having a plurality of subscribers stations, a switching device individual to said party line having digit register switches, means operative subsequent to said digit registers being positioned by groups of impulses from a subscribers station on said party line for transmitting in uninterrupted succession the number of impulses for selecting the wanted subscribers station.

7 In a telephone system, a party line having a plurality ot subscribers stations, a relay mechanism and a stepping switch individual to each of said subscribers stations, a switching device individual to said party line for transmitting impulses over said line and for registering the called subscribers number7 means responsive to one of said subscribers stations seizing said party line for causing said switching device to send an impulse over said line to operate said stepping switches at all of said subscribers stations to prevent other subscribers from seizing said party line, means operative subsequent to the registration of the called number for sending a series of impulses corresponding to the setting of the digit register to operate all of said stepping switches in synchronism, means responsive to the operation -of said switches for signalling only the called station, and means responsive to the answering of the called party for connecting the called station to said party line.

8. In a telephone exchange, a party line having a plurality of subscribers stations, a switching device individual to said party line and capable of transmitting alternating current impulses over said line, another telephone eXchange having access to said switching device and said party line, a busy subscribers station on said party line, means responsive to a call from said other exchange for disconnecting said busy subscribers station, and means operative subsequent to said busy subscriber hanging up his receiver for selecting the wanted subscriber on said party line.

In witness whereof, I hereunto subscribe my name this 12th day of March, A. D. 1930.'

ROBERT KRUSE.

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